If you haven’t discovered Pandora yet, you are in for a great surprise. One of my favorite sites, it allows you to type in whatever artist you are in the mood for hearing, allowing it to create a playlist or “channel” for you of other artists that have the same sound.
For example, if you type in John Mayer, you will hear John Mayer, Dave Matthews, maybe even some Snow Patrol or Mat Kearny.
If you are tired of just listening to online stations at work, check out this site, its pretty sweet. It does seem to suck up some bandwidth though, sort of like youtube, so just close it out for 20 minutes or so if people start complaining about how slow the internet is today.
Lastly, just save yourself the frustration and register as soon as you decide you like it or it will keep asking you to register which, lets be honest, is really annoying.